Is it me, or all the plans made by the strategist kid so far have always been horribly flawed?
That's what happens when the characters are smarter than the writer.
All of the war tactics and etc this manga displayed so far are flawed and kinda stupid at best.
If you want to write medieval battles with cavalry, archers, footsoldiers and etc but you don't want to research said tactics in depth, just take some random small-scale battle from history and flow with that, rewrite some things to take into account magic and thats alright.